The present invention is directed to printing sleeves for offset or flexographic printing, and more particularly to printing sleeves having a sound dampening feature that attenuates noise during mounting and dismounting of the sleeve from a support cylinder.
An offset printing unit has a plurality of rotatable cylinders, including at least one plate cylinder and at least one corresponding blanket cylinder. The plate cylinder carries a printing plate having a surface on which an inked image is defined. The blanket cylinder carries a printing blanket. The plate on the plate cylinder transfers the inked image to the blanket on the blanket cylinder at a nip between the plate cylinder and the blanket cylinder when the cylinders rotate. The blanket on the blanket cylinder subsequently transfers the inked image to the material being printed, such as a web of paper.
Printing blankets have conventionally been formed as flat sheets which are then mounted on a blanket cylinder by wrapping the sheet around the blanket cylinder. More recently, printing blankets in the form of hollow tubular sleeves have become more prevalent. Such sleeves are mounted on a blanket cylinder by sliding the sleeve telescopically over the blanket cylinder. The sleeve and the blanket cylinder are designed so that the sleeve is receivable over the blanket cylinder with an interference fit.
The blanket cylinder is equipped with air flow passages and openings to direct a pressurized flow of air over the blanket cylinder. When the sleeve is located over the air flow openings in the blanket cylinder, the pressurized flow of air expands the sleeve diametrically. The expanded sleeve can be moved axially onto, or off of, the blanket cylinder when in its expanded condition. When the pressure is relieved, the sleeve contracts diametrically against the blanket cylinder and thus establishes an interference fit with the blanket cylinder. Flexographic printing sleeves have also been developed and are mounted onto and dismounted from support cylinders in much the same manner as offset sleeves.
One problem with such sleeves is that the compressed air that is used in mounting and dismounting the sleeves from the cylinders can create a whistle or other loud noise during the procedure. The sleeve ends may also vibrate causing additional noise to emanate during mounting and dismounting. In some instances, press operators may need to don ear protection gear to avoid injury. One solution to the problem has been proposed by Vrotacoe et al, U.S. Pat. No. 5,215,013. Vrotacoe et al describe a blanket sleeve having a damping ring made of a resinous material that is adhered to the interior wall of the sleeve near and end thereof. The ring is designed to reduce vibrations caused by the flow of pressurized air and attenuate noise associated with mounting and dismounting of the sleeves.
Another solution has been proposed by Boucher et al, U.S. Pat. No. 6,347,586 B1. Boucher et al adhere a sound dampening material on the outer surface of the blanket cylinder such that the material engages the interior wall of the printing sleeve during mounting and dismounting thereof. The preferred material for use is a non-woven, fibrous material such as the xe2x80x9chookxe2x80x9d portion of a VELCRO(copyright) closure.
However, the proposed solutions have not been entirely successful in solving the problem. Accordingly, there remains a need in the art for a printing sleeve having a sound dampening feature that attenuates noise during mounting and dismounting of the sleeve from a support cylinder.
The present invention meets the need in the art by providing an easy to manufacture and install sound dampening pad for a printing blanket sleeve that effectively attenuates noise emanating from the sleeve during air pressurized mounting and dismounting thereof.
In accordance with one aspect of the present invention, a printing blanket sleeve for mounting onto an underlying cylinder using a pressurized flow of air through at least one flow opening in said cylinder is provided. The sleeve comprises a cylindrical base having first and second ends and at least one additional layer on the base having a printing surface. As is typical in this art, the blanket sleeve may include additional reinforcing, stabilizing, and/or compressible layers. The sleeve base has an inside diameter that is less than the diameter of the underlying cylinder but which is expandable under the influence of pressurized air such that the inside diameter of the sleeve base temporarily has a diameter that is greater than the diameter of the underlying cylinder.
The printing blanket sleeve includes a sound dampening pad mounted on at least one of the ends of the printing blanket sleeve for attenuating noise associated with the mounting and dismounting of the printing blanket sleeve. The sound dampening pad comprises a flexible material extending around substantially the inner circumference of the sleeve base and over an end of the printing blanket sleeve.
In a preferred form, the sound dampening pad has a generally J-shaped configuration, in which the inner radius of the xe2x80x9cJxe2x80x9d is in contact with the inner circumference of the sleeve base and an outer surface of an end of the sleeve. Generally, the shorter leg of the xe2x80x9cJxe2x80x9d has a thickness that is less than the overall thickness of the printing blanket. Also, the longer leg of the xe2x80x9cJxe2x80x9d is not so long as will interfere with the end of the blanket cylinder onto which the blanket sleeve is mounted. A suitable thickness for the legs of the sound dampening pad is from about 0.03 to about 0.05 inches (0.76 to about 1.27 mm), and most preferably about 0.042 inches (1.07 mm).
The sound dampening pad may be comprised of natural or synthetic rubber or a thermoplastic polymer having the requisite flexibility for installation of the pad. In a preferred form, the sound dampening pad includes an adhesive on an inner surface thereof to secure the pad to the printing blanket sleeve. In one embodiment, the adhesive is a pressure sensitive adhesive in the form of a double-sided adhesive tape.
In accordance with another aspect of the invention, a sound dampening pad is provided and comprises a flexible polymeric material having a generally J-shaped configuration and inner and outer surfaces. At least a portion of the inner surface of the J-shape includes a pressure sensitive adhesive thereon. Preferably, the sound dampening pad comprises natural or synthetic rubber or a thermoplastic polymer having the requisite flexibility for mounting it in the sleeve.
In a preferred form, the pressure sensitive adhesive comprises a double-sided adhesive tape in which the exposed surface of the double-sided adhesive tape includes a release liner thereon. In another embodiment, the double-sided adhesive tape includes a foam core.
In accordance with another embodiment of the invention, a method for mounting a sound dampening pad to a printing blanket sleeve is provided. The method comprises providing a sound dampening pad comprising a flexible polymeric material having a generally J-shaped configuration and inner and outer surfaces with at least a portion of the inner surface of the J-shape including a pressure sensitive adhesive thereon, adhering the inner surface of the sound dampening pad to the inner surface of the printing blanket sleeve such that the sound dampening pad extends substantially about the inner circumference of the sleeve and over the end of the sleeve.
In a preferred form, the sound dampening pad is in the form of a length of material and the pad is cut to have a length of substantially the inner diameter of the sleeve prior to installation. Preferably, the inner radius of the J-shaped configuration is placed in contact with the inner circumference of the base and an outer surface of an end of the sleeve and secured thereto. The sound dampening pad provides the additional advantages of aiding in the installation of the blanket sleeve. The edges of the pad overlap the sharp edge of the base of the sleeve and provide protection to an operator""s hands as the sleeve is pushed onto and pulled off of the cylinder.
Accordingly, it is a feature of the present invention to provide an easy to manufacture and install sound dampening pad for a printing blanket sleeve that effectively attenuates noise emanating from the sleeve during air pressurized mounting and dismounting thereof. Other features and advantages of the invention will become apparent from the following detailed description, the accompanying drawings, and the appended claims.